This invention relates generally to methods and systems for recovering noble metals, and particularly to high efficiency methods and systems for recovering noble metals from geologic bodies of water such as fresh water rivers and lakes, brackish estuaries, and salt water seas and the oceans.
It has long been known that the seas of the world possess an abundance of noble metals such as gold, silver and platinum. To date, however, no industry has yet to evolve for the mining of these precious metals since no economically efficient method has yet been devised for their extraction. The present invention is believed to constitute the discovery of an economically efficient manner in which to harvest noble metals and specifically gold from the sea.
Today there does, of course, exist many methods of recovering noble metals from dilute aqueous solutions under laboratory conditions. For example, in U.S. Pat. No. 2,371,119 a process is disclosed from recovering precious metals from aqueous liquids through the use of anion absorption materials. Since the issuance of this patent in 1942 interest in the use of anion absorption materials has remained as evidenced by the issuance in 1976 of U.S. Pat. No. 3,994,719 which teaches the use of a weakly basic anion absorption material composed of thiourea group containing synthetic resins of a crosslinked, macroporous, vinyl-aromatic base polymer of monovinyl and polyvinyl compounds. U.S. Pat. No. 3,006,756 discloses other such basic absorption materials as does U.S. Pat. No. 3,736,126 which utilizes polymers of lower aliphatic esters of acrylic acid as an absorption bed for the recovery of gold from seawater under laboratory controlled conditions after the seawater has been acidified and chloride ions added thereto to complex the gold.
Along with anion absorption materials has existed the use of anion exchange materials such as that disclosed in U.S. Pat. No. 3,001,868 wherein a nitrogenous anion exchange resin having both weakly and strongly basic amine exchange groups is utilized. U.S. Pat. No. 3,817,745 also discloses the use of crosslinked polymeric N-vinyl-amide and a polyhydroxyaryl compound for this type recovery. U.S. Pat. No. 3,473,921 further teaches the use of chloromethylated styrene divinylbenzene resin reacted with throurea as an ion exchange resin of the basic anion exchanger type for the recovery of gold. In general these recoveries are from cyanide solutions, bearing gold compounds.
In addition to laboratory methods of recovering noble metals from dilute solutions work has also heretofore been done in direct attempts at obtaining precious metals present in but trace quantities from seawater. U.S. Pat. No. 3,155,454, for example, discloses a method of recovering silver from seawater by percolating it through a bed of magnesium ammonium phosphate. U.S. Pat. No. 3,565,608 further teaches such use of water insoluble ethylene copolymer containing carboxylate and/or amide groups. In this latter patent the material is formed as a film which is drug as by a ship through gold containing waters or attached to a buoy located within a current. Recovery of noble metals found in ocean floor nodule ores by halidation has been suggested by U.S. Pat. No. 3,940,470.
It is thus apparent that heretofore materials per se have been developed which have been capable of recovering noble metals from various dilute solutions. Nevertheless, none of these have ever found commercial use in sea mining because they have been economically inefficient. For example, it is of little commercial value to recognize that recovery is possible provided that the sea water first be treated due to the vast quantities of sea water required for processing. Without a practically workable material knowingly available for this usage, it follows that little work has been accomplished in developing a system for such to perform on a workable basis.
Accordingly it is a general object of the present invention to provide a high efficiency method and system for recovering noble metals from geologic bodies of water.
More specifically, it is an object of the invention to provide commercially practical, efficient and economic methods and systems for recovering gold and other noble metals from geologic bodies of water such as fresh water rivers and lakes, brackish estuaries and salt water seas and the oceans.